The United States has fully bounced back from a period of slow growth in June. Following fairly strong July numbers, we’re now seeing a big gain of five million new monthly active users in August for Facebook’s home country.

Seasonality can serve to explain some of what’s happening in the US — early summer has traditionally been a slow period for social networks and other youth-dominated sites, as high school and college kids take a break from school. But there appears to be more to the story.

The overall penetration level of the US has continued to creep up through monthly volatility, now standing at 43.8 percent overall. The common wisdom has held that US growth would likely level out at around 40 percent penetration. That hasn’t happened yet, with the US continuing to provide the strongest gains for Facebook more often than not. More>>